The Rule

Affect is usually a verb. Effect is usually a noun.

That's it. That handles 95% of cases. "The weather affects my mood." "The weather had an effect on my mood."

The Test

If you can replace the word with "influence," use affect (verb). If you can replace it with "result," use effect (noun).

  • "The new policy will affect hiring." → "The new policy will influence hiring." ✓
  • "The new policy had a major effect." → "The new policy had a major result." ✓

The Exceptions

There are two edge cases, and they're rare enough that most people never encounter them:

Effect as a verb means "to bring about", used almost exclusively in formal writing. "The president sought to effect change." This is uncommon and often sounds stiff. When in doubt, use "bring about" or "cause" instead.

Affect as a noun is a psychology term meaning emotional expression. "The patient displayed flat affect." Unless you're writing clinical notes, you'll never need this.

Quick Reference

| Sentence | Correct Word | Why | |---|---|---| | The cut will ___ profits | affect | verb: influencing something | | The ___ was immediate | effect | noun: the result | | This will ___ everyone | affect | verb: influencing people | | Side ___s include drowsiness | effect | noun: results |

When You're Still Unsure

Default to the verb/noun rule. If the word is doing something (a verb), it's almost certainly "affect." If it's a thing (a noun), it's "effect." You'll be right the vast majority of the time.